When Treasury Secretary James A. Baker III was asked recently what progress had been made in finding a replacement for World Bank President A. W. Clausen, he responded that he didn't have to worry about that for another seven months or so.

It's true, of course, that Clausen's five-year term isn't up until June 30, 1986. But as Chase Manhattan Bank Chairman Willard C. Butcher said here the other day, Clausen's successor ought to be named as soon as possible if Baker is serious about a new role for the World Bank as part of the debt initiative he put forward in early October in Seoul.

Clausen, as Butcher suggested, is in the difficult position of being a lame duck at the very time that the bank is being asked to lead the way in the transition from an austerity-oriented policy for the Third World, guided by the International Monetary Fund, to one emphasizing the need to rekindle growth.

There is no time to waste. Mexico, which had been held up as the shining example of the success of the case-by-case approach of the IMF, is in trouble again. Just paying the interest on its $96 billion debt will cost Mexico $10 billion this year, or 40 percent of Mexico's gross earnings from exports. And Mexico isn't considered a leading candidate for help from the Baker plan.

In Seoul, Baker drew a diagram for a new policy to deal with the latest stage of the Third World debt crisis, and referred to it as a "three-legged stool."

The first leg of the Baker stool calls for the World Bank and the regional development banks to boost their loans by 50 percent -- from $6 billion to $9 billion over the next three years -- to 15 major debtor nations -- mostly in Latin America -- that otherwise might default.

At the same time, commercial banks are being asked to pledge a $20 billion boost in their loans to the same group of countries. That's the second leg.

And the third leg would be a commitment on the part of the major borrowers -- presumably starting with Argentina -- to comprehensive reform of their economies along market-oriented lines. Each leg of the stool depends on the other, as Baker himself stressed, and that's what puts some urgency on getting the World Bank ready for new responsibilities.

Butcher's idea is that the United States and the other major powers in the World Bank should waste no more time in making their selection of the new president. "I'd like to see a bridge in the succession process built right now," Butcher said, "even if the new guy would just serve in an advisory role to Clausen . We certainly shouldn't wait until June." Baker's plan has been widely praised, along with his effort to devalue the dollar, as a sign of a new maturity in American economic relations. Clearly, Baker was suggesting that the prior debt strategy wasn't adequate, and implied that, after a change in the bank presidency, the United States would support a general capital increase for the World Bank that would add significantly to its lending power.

He also recognized that big commercial banks, having been stung by difficulties collecting on massive Third World loans, would not increase their commitments voluntarily. In a recent speech in Columbia, S.C., IMF Managing Director Jacques de Larosiere revealed that commercial bank loans to Latin America, which averaged $41 billion a year from 1980 to 1982, had plunged to a only $1 billion this year.

But since Baker unveiled the "three-legged stool" in Seoul, it hasn't materialized. It remains a mere blueprint as Baker, Assistant Treasury Secretary David Mulford and Federal Reserve Board Chairman Paul A. Volcker jet between Washington, New York, Europe and Latin America trying to get commercial banks and the debtor countries to make the necessary commitments.

This, then, would seem to be an opportune time to make more visible the third leg of the stool, the one that the Reagan Administration has the best ability to influence: the new role Baker sketched out for the multilateral development banks. And that should start by naming a new World Bank president.

This might offset some of the skepticism in the banking and financial community on other aspects of the Baker plan. In a paper on the Latin American debt situation prepared for a conference at the Wye Plantation in Maryland, Richard E. Feinberg of the Overseas Development Council notes that the scope of the Baker plan doesn't match the size of the problem, as defined by Baker himself.

"The plan was announced unilaterally, without consulting the debtors being asked to undertake revolutionary changes in their political economies, or even other industrial countries whose banks and taxpayers will be expected to contribute," Feinberg said.

Moreover, Baker's choice of supply-side rhetoric raises the possibility that "a fortified creditor cartel . . . led by the World Bank" might try to impose a particular ideology in Latin America, threatening a new phase of the political confrontation between North and South, Feinberg wrote.

For all of these reasons, no time should be lost in reorganizing the bank's mission under a new president acceptable to the debtor countries, who can bring the kind of leadership and dynamism that the Reagan administration contends was lacking in Clausen. De Larosiere noted in his speech that the large capital outflow from Third World countries continues to be a concern. Some certainty about who is to run the World Bank, with actions to back up the Baker rhetoric, would seem to be an immediate requirement.